The server sends an EOB_ACK packet a certain number of times, that
depends on its length.

The EOB is the most time-wasting point of the whole transfer, and it
gets A LOT worse (10 times) if the EOB_ACK packet is lost (this occurs
with increasing probability as the dimension of a block and of the
single packets increases).

TODO: find a more appropriate rule to determine the number of retx, and
use an identifier for the EOB ACK so that the client does not retransmit
data due to multiple reception of a single EOB_ACK.